The Organisation for Security and Co-operation in Europe (OSCE) - which contributed to the 230 foreign monitors for the polls - acknowledged that there were some irregularities during the poll that should be investigated.

However, OSCE Ambassador Robert Barry said on Sunday "the candidates' demand to nullify the election is unjustified and would not do service to the people of Afghanistan who came out yesterday, at great personal risk, to vote".

Meanwhile, the Free and Fair Election Foundations of Afghanistan (Fefa) - the single largest observer group - said that "a fairly democratic environment has generally been observed in the overall majority of the polling centres".

But vote observers were deployed thinly around Afghanistan's 25,000 pollings stations because of security fears, and full monitoring operation was not attempted.

The UN, which helped organise the poll, has praised the "massive" turnout in the election.

More than 10 million people were registered to vote, many of them refugees living in Pakistan and Iran.

The ousted Taleban regime has dismissed the election as foreign-sponsored and has said it will continue its armed struggle.

However, fears that militants linked to the Taleban would carry out their threat to sabotage the vote appear to have been largely unfounded.

Ink stains

The vote was marred by reports that an ink used to stain voters' fingers to prevent them from casting their ballot more than once could be washed away.

If the Afghan people have voted for me, no horse-trading

Interim president Hamid Karzai

This prompted all the candidates opposing interim President Hamid Karzai - the favourite to win the race - to call for the election result to be annulled.

However, several candidates appear set to drop calls for a vote boycott.

Their representatives told the BBC they would instead accept the findings of an independent inquiry into alleged irregularities.

Mohammed Mohaqeq, one of Mr Karzai's main rivals, was the first to announce he was withdrawing his backing for the boycott.

The indelible ink had to be applied to the cuticle of the voter's fingernail

Mr Mohaqeq said he wanted a UN commission to investigate the election and he would accept its ruling on its legitimacy.

Other candidates are also withdrawing calls for a boycott in favour of a more conciliatory approach, according to the BBC's Andrew North in Kabul.

President Karzai criticised the move as an affront to the hopes of the millions of Afghans who braved bad weather and the threat of terrorism to turn out to vote.

He was adamant there would be no back-room deals to solve the row.

"If the Afghan people have voted for me, no horse-trading. The horse-trading times are over in Afghanistan," he told a news conference.